The present invention relates to trunking and particularly, but not exclusively, to waterproof trunking used for carrying electrical cables.
The carrying of electrical cables in a network of trunking is used in many industries. In the food, beverage and pharmaceutical industries, where hygiene is of paramount importance, stainless steel trunking is regularly used. It is important that such trunking is easily cleaned and that places where dirt may gather, and infestation may occur, are kept to a minimum. In some situations it is necessary to provide waterproof trunking. For example, where trunking is located near a high ceiling the preferred method of cleaning maybe to direct a jet of water at the trunking from the ground.
An example of trunking of the prior art is shown in FIGS. 1 and 2. From the figures it can be seen that trunking section 10 has a lip 12 extending away from the remainder of trunking section 10. Lip 12 extends outside the main body of trunking section 10 because there is a danger that water can leak around the thread of screw 14 and through seal 16. If lip 12 extended within the internal volume of trunking section 10 there is a danger that the cables therein would become wet. However, the lip 12 makes the trunking difficult to clean and when in use, the lid 18 and the base of the screws 14 create numerous dirt traps, making this sort of trunking unsuitable for circumstances where very high hygiene standards are required. Furthermore, this form of trunking is unsuitable for installation against a wall as a gap, the width of the lip 12, must exist between the external wall of the trunking section 10 and the wall that is located adjacent. This gap increases the difficulty in cleaning this form of trunking.
An alternative trunking system used in the above mentioned industries is shown in FIG. 3. In such a system, a coupling for joining two lengths of trunking 1 and 2, utilises an internal fixing mechanism consisting of a coupling 5, having slots 6 and 7 cut therein. These slots align with threaded studs 3 and 4 onto which bolts (not shown) are tightened thus holding the coupling 5 in engagement with trunking lengths 1 and 2. This system provides a smooth joint between the trunking sections 1 and 2, therefore allowing the outside surfaces of the trunking to remain free from dirt traps. However, this system has only four fixing points to join two sections of trunking, and as a result such joints in a trunking system are unsuitable for spanning a distance greater than a single length of trunking unsupported. Furthermore, if one or more of the four fixing points are not sufficiently tightened the trunking sections can be easily separated.
Preferred embodiments of the present invention seek to overcome the above described disadvantages of the prior art.